I've tried Voicetext.jp and Google's text to voice service to read this
四中の
It reads something like
Yon-chū no
But Google suggested this romanization, which left me doubtful
Shi-chū no
So, I have been redirected to a similar question discussing why there is different pronunciations of the numbers 4, 7 and 9 (maybe there's more).
From the given answers, I can't decide how to read things like
足立区立第四中学校
Because none of the examples addressed there were close enough to school names, rankings and such...